Pressure sensitive shrink label

ABSTRACT

A label for application to a surface having at least one compound curve is provided. The label comprises a heat shrinkable film having an inner surface and outer surface and a layer of pressure sensitive adhesive on the inner surface of the heat shrinkable film.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of PCT/US08/59397 filed Apr.4, 2008, which claims priority from provisional applications U.S. Ser.No. 60/910,282 filed Apr. 5, 2007 and U.S. Ser. No. 60/938,019 filed May15, 2007, the entire disclosures of which are incorporated herein byreference, and is related to co-pending U.S. application Attorney DocketNo. AVERP4032WOUSB (U.S. Application No. ______) filed on Sep. 25, 2008.

TECHNICAL FIELD

This invention relates to pressure sensitive shrink labels. Morespecifically, the invention relates to pressure sensitive labels thathave superior conformability to containers having complex shapes andmethods for applying such labels.

BACKGROUND

It is common practice to apply labels to containers or bottles toprovide information such as the supplier of the container or thecontents of the container. Such containers and bottles are available ina wide variety of shapes and sizes for holding many different types ofmaterials such as detergents, chemicals, personal care products, motoroil, beverages, etc.

Polymeric film materials and film facestocks have been described for useas labels in various fields. Polymeric labels are increasingly desiredfor many applications, particularly clear polymeric labels since theyprovide a no-label look to decorated glass and plastic containers. Paperlabels block the visibility of the container and/or the contents in thecontainer. Clear polymeric labels enhance the visual aesthetics of thecontainer, and therefore the product, and are growing much faster thanpaper labels in the package decoration market as consumer productcompanies are continuously trying to upgrade the appearance of theirproducts. Polymeric film labels also have superior mechanicalproperties, such as tensile strength and abrasion resistance.

Traditional pressure sensitive adhesive (PSA) labels often havedifficulty adhering smoothly to containers having curved surfaces and/orcomplex shapes without wrinkling, darting or lifting on the curvedsurfaces. The label size of typical PSA labels is limited to no largerthan ¼ inch away from the edge (beginning) of curvature of a containeror article. Shrink sleeve labels have typically been used on these typesof compound containers. Labeling operations are carried out usingprocesses and methods that require the formation of a tube or sleeve ofthe heat shrink film that is placed over the container and heated inorder to shrink the film to conform to the size and shape of thecontainer. Alternatively, the containers are completely wrapped with ashrink label using a process wherein the shrink film is applied to thecontainer directly from a continuous roll of film material and then heatis applied to conform the wrapped label to the container. However, labeldefects can occur during labeling operations of simple or compoundshaped bottles during application or in post application processes.These misapplied labels result in high scrap or extra processing stepsthat can be costly.

The present invention provides a pressure sensitive adhesive label thatcan be applied to containers and articles on complex shapes and compoundcurves with less material required and less cost than for shrink sleeveor shrink wrap labels. In addition, the labels of the present inventionenable the user to expand the billboard or graphics region oftraditional pressure sensitive labels on containers and articles havingcomplex shapes and/or compound curves.

SUMMARY

A label for application on a curved or nonplanar surface comprising aheat shrink film and a pressure sensitive adhesive is provided. In oneembodiment, there is provided a pressure sensitive adhesive label forapplication on a surface having at least one compound curve, the labelcomprising: a heat shrinkable film having an inner surface and outersurface, and a machine direction and a transverse direction, the filmhaving an ultimate shrinkage S in at least one direction of at least 10%at 90° C., wherein the shrinkage in the other direction is S±20%; and alayer of pressure sensitive adhesive on the inner surface of the heatshrinkable film. The shrink film has moderate and balanced shrink inboth the machine direction and the transverse direction. In oneembodiment, the film has an ultimate shrinkage S in at least onedirection of at least 10% at 90° C., and the shrinkage in the otherdirection is S±10%. The label may further include a release linerremoval adhered to the adhesive layer.

There is also provided an article bearing a label comprising: an articlehaving a surface comprising at least one compound curve; and a pressuresensitive label comprising a heat shrinkable film having an innersurface and outer surface, and a layer of pressure sensitive adhesive onthe inner surface of the heat shrinkable film, wherein the label isapplied to at least one compound curve.

A method of applying a label to an article wherein the article has asurface having at least one compound curve is provided. The methodcomprises: (a) providing an article having a surface comprising at leastone compound curve; (b) providing a label comprising (i) a heatshrinkable film having an inner surface and outer surface and (ii) alayer of pressure sensitive adhesive on the inner surface of the heatshrinkable film, wherein the label has a central portion and aperipheral portion; (c) contacting the adhesive layer of the centralportion of the label with the article; (d) applying pressure to thelabel in an outward direction from the central portion to the peripheralportion, wherein at least a portion of the label is applied to at leastone compound curve of the article; and (e) applying heat to at least aportion of the label to shrink at least that portion of the label andadhere the label to the article. After or during the application ofheat, the label may be further compressed or wiped down to fully adherethe label to the article and eliminate any remaining defects in thelabel.

In one aspect of the invention, there is provided a method of applying alabel to an article, the method including the steps of providing anarticle having a surface comprising at least one compound curve;providing a label comprising (i) a heat shrinkable film having an innersurface and an outer surface; and (ii) a layer of pressure sensitiveadhesive on the inner surface of the heat shrinkable film, wherein thelabel has a first edge and a contact region; contacting the adhesivelayer in the contact region of the label with the article; and applyingheat and pressure simultaneously to the label in a direction from thecontact region to the first edge such that the first edge of the labeladheres to the article and the label shrinks to conform to the compoundcurve of the article, wherein the heat and pressure are applied by atleast one hot air knife assembly comprising a source of heated air, aflow control mechanism and one or more hot air knife slots.

In one embodiment, the label includes a center and a second edgeopposite the first edge, and the contact region is proximate to or inthe center of the label. In another embodiment, the label includes asecond edge opposite the first edge and the contact region is proximateto the second edge of the label.

Heat and pressure may be applied to the label by a hot air knifeassembly that includes at least two hot air knife slots that rotateoutwardly from the center of the label to the first and second edges toadhere the label to the article.

In one embodiment of the method of the present invention, a first hotair knife slot applies heat and pressure to the center of the labeloutwardly to the first edge of the label, and a second hot air knifeslot applies heat and pressure to the center of the label outwardly tothe second edge of the label. The article may be rotated about 180°prior to the application of heat and pressure by the second hot airknife slot to the label.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 illustrates a front view of a container to which the label of thepresent invention has been applied as compared to prior art pressuresensitive labels.

FIG. 2A to 2D illustrates the labeled container before and after theapplication of heat to the label.

FIG. 3A to 3D illustrate embodiments of containers having complex shapesand compound curves to which the label of the present invention isapplied.

FIG. 4A and 4B illustrate front views of embodiments of containershaving irregular surfaces.

FIG. 5 is a three dimensional view of a portion of a labeled articlehaving a compound curve.

FIGS. 6A-6D schematically illustrate the process of applying the labelto an article having a compound curve.

FIGS. 7A and 7B schematically illustrate an embodiment of the process ofapplying a label to an article wherein a walking beam is used.

FIGS. 8A and 8B are schematic views of an air knife assembly forsimultaneously applying heat and pressure to a label.

FIGS. 9A-9E are schematic views of a process for applying a label to anarticle using multiple air knife slots.

DETAILED DESCRIPTION

Pressure sensitive adhesive labels are provided that can improve theappearance of labeled containers and articles by conforming to thecontours of the container or article and by providing an enlargedbillboard appearance. End users and product designers must currentlyalter their designs to accommodate the limitations of traditionalproduct decorating technologies. The labels of the present inventionprovide the designers with more freedom in product designs to createmore shelf appeal and to carry more information.

Containers and articles with compound curves typically have to be fullywrapped with shrink film in order to label or decorate the article. Thelabels of the present invention are capable of expanding the label overcomplex curves without having to fully wrap the article. This partiallabel coverage impacts the product cost as well as the productappearance. Typical pressure sensitive labels cannot be applied tocontainers and articles without undesirable darting and wrinkling of thelabel. “Darting” is defined as the accumulation of excess label materialthat rises up away from the article to which the label is applied.

The labels of the present invention provide significant processingadvantages over traditional shrink labels. For example, the pressuresensitive shrink labels of the present invention allow for moretraditional printing and secondary processes such as foils and hotstamping. Where typical shrink labels must be subsurface printed, thelabels of the present invention can be surface printed, which enhancesthe color quality, sharpness and texture of the printed image. The labelfilm may be printed by water flexographic, UV flexographic, UVletterpress, UV screen, solvent gravure and hot foil stamp.

The pressure sensitive labels comprise (a) a heat shrinkable polymericfilm having an inner surface and an outer surface and a machinedirection and a transverse direction; and (b) a layer of pressuresensitive adhesive on the inner surface of the heat shrinkable film. Theshrinkage of the heat shrinkable polymeric film is balanced in themachine direction and the transverse direction. In at least onedirection, the ultimate shrinkage (S) is at least 10% at 90° C. and inthe other direction, the shrinkage is S±20%. As an illustration ofbalanced shrinkage, if the shrinkage in the machine direction is 40% at105° C., then the shrinkage in the transverse direction is 40%±20%, orwithin the range of 20% to 60% at 105° C. In one embodiment, theultimate shrinkage (S) is at least 10% at 90° C. and in the otherdirection, the shrinkage is S±10%. As used herein, the term “ultimateshrinkage” means the maximum shrinkage the film is capable of achievingat a particular shrink temperature, as measured by ASTM Method D 1204.

The labels are not provided as a shrink sleeve or tube that encapsulatesthe entire article or as a shrink wrap label that wraps around thearticle and forms a seam wherein the ends of the label meet. The presentlabels may be provided in a variety of shapes to suit the article orcontainer to which they are applied, giving the container designergreater latitude in container configuration and label design than withtraditional pressure sensitive labels or with shrink wrap or shrinksleeve labels. The labels may be cut into the desired shape by any knownmethod, including, for example, die cutting and laser cutting. In oneembodiment, the label is die cut to a specific configuration thatcompensates for the shrinkage of the label and the shape of the articleto which it is applied.

Because the label is conformable, the billboard or graphics area of thelabeled container can be extended further onto the container edges andonto compound curved areas of the container. The label may be 10% to 30%larger than a standard PSA label. As used herein, the term “compoundcurve” means a surface having no direction for which there is nocurvature. For example, the surface of a sphere or the surface of anellipsoid has curvature in every direction, and therefore has compoundcurves. A cylinder, on the other hand, has a surface for which there isat least one direction for which there is no curvature. Thus, a simplecylinder does not have compound curves.

FIG. 1 illustrates the expanded billboard area of the pressure sensitiveshrink label of the present invention. Bottle 10 has pressure sensitiveshrink label 12 adhered thereto. The dashed line 14 indicates the outerboundary of standard pressure sensitive labels. A standard (i.e.,non-shrink) pressure sensitive label cannot extend onto the areas of thebottle having the compound curves 16 (the area between the inner dashedline and the outer solid line). When label 12 is initially applied tothe bottle 10, darts and pleats may form near the perimeter of the labelin the areas of the bottle having compound curves 16.

Once the pressure sensitive label is applied to the container, heat isapplied as needed to eliminate any label application defects such asdarts, edge lift and wrinkles. In one embodiment, pressure and/or wipedown may be used in addition to the application of heat to eliminate anydefects.

Referring to FIGS. 2A-2D, the present label and method for applying thelabel are illustrated. In FIGS. 2A and 2B, a label 12 that includes ashrink film having a continuous layer of pressure sensitive adhesiveapplied thereto is applied to a container 10 having compound curvesaround the circumference of the container, and then wiped down. No heatis applied to the label. The label 12 extends onto the compound curves16 where darts 18 are formed near the perimeter 20 of the label. FIGS.2C and 2D show the labeled container of FIGS. 2A-2B after heat isapplied to the label. The darts 18 have been eliminated and the label 12conforms to the compound curves of the container 10 near the labelperimeter 20 without any defects.

The article or container to which the label is applied can be providedin a variety of forms or shapes. Non-limiting examples of suitablearticles include containers with and without closures, trays, lids,toys, appliances, etc. The article or container may be made of anyconventional polymer, glass, or metal such as aluminum. Examples ofsuitable polymeric materials include high density polyethylene (HDPE),low density polyethylene (LDPE), polyethylene terephthalate (PET),polypropylene (PP), polyvinyl chloride, polycarbonate, nylon,fluorinated ethylene propylene, polystyrene, etc. The article orcontainer can be made by a number of various processes known in the art,such as blow molding, injection molding, thermoforming, rotationalmolding and the like.

Useful containers include, for example, a bottle having a closure on thetop of the bottle, an upside down bottle having a closure on the bottomof the bottle, a bottle with a pump dispenser or a foaming dispenser, atube with a closure and a tottle with a closure.

The container or article may have a transparent appearance. In oneembodiment, the container or article has a translucent appearance. Thetranslucent appearance can be achieved by, for example, treatments ofthe transparent container or article, the addition of ingredients suchas dyes and pearlescent agents to base polymers, the use ofpolypropylene and/or polyethylene that are mixed with clarifying agents.The treatments include, for example, spray coating, sandblasting, andmold surface treatment.

The container or article may include aesthetic features, including, forexample, textures, embossing, lenticular lens, colors, holograms,frosted or matte color, etc. The surface of the container or article maybe treated prior to application of the label. For example, the surfaceof the container or article may be flame treated or a primer coating maybe applied.

FIGS. 3A, 3B and 3C each illustrate a container having a complex shapeand compound curves. FIG. 3A is a front view of a container 30 a havinga symmetrical, spherical shape wherein the container has a taperedconcave area 32 at the top and a wider convex area 33 toward the bottom.Typically, a shrink sleeve would be used to provide a functional labelfor this container. With the present invention, a pressure sensitiveshrink label 31 can be smoothly applied to container 30 a without theappearance of label defects. FIG. 3B is a front view of a container 30 bhaving an asymmetrical shape wherein one side of the container has botha concave area 34 and a convex area 35 and the opposing side curves in asubstantially similar manner along the length of the container. Theconventional method of labeling container 30 b would be to apply ashrink sleeve label to conform to the complex shape of the container. Apressure sensitive shrink label 31 can be applied to the container 30 bto provide sufficient billboard area with much less label material. FIG.3C is a front view of a container 30 c that is an upside down bottlehaving a closure 36 at the bottom and label 31 applied to the frontsurface. FIG. 3D is a side view of container 30 c. The areas 37 withinthe dashed lines indicate the outer boundaries of standard pressuresensitive labels that can be applied to the container. The complex shapeof this container requires two separate standard pressure sensitivelabels to decorate the container, as the application of one continuousstandard pressure sensitive label would result in the formation of dartsand pleat defects. Pressure sensitive shrink label 31 can cover a muchlarger area, which provides more design options for the productdesigner.

FIGS. 4A and 4B each illustrate a container having an irregular surface.FIG. 4A is a front view of a container 40 a having raised ridges 42along one side of the container. The opposing side of the container hasa smooth surface. FIG. 4B is a front view of a container 40 b havingcircumferentially recessed rings 43 along the length of the container.It should be noted that cylindrically shaped articles having areas ofcompound curves such as containers 40 a and 40 b are not excluded fromthe articles claimed herein.

FIG. 5 is a schematic three dimensional view of a portion of a containerto which the label has been applied. The container 50 has surfacecomprising a compound curve. Label 52 is applied to the container andcovers a portion of the compound curved area. Line 54 indicates theouter boundary to which typical pressure sensitive labels can be appliedwith out the formation of defects in the label. Area 56 indicates theexpanded billboard area that is obtainable with the present labelswithout the formation of defects such wrinkles, edge lift or darts.

Shrink Film

The polymeric films useful in the label constructions of the presentinvention possess balanced shrink properties. The balanced shrinkproperties allow the film to tighten darts and wrinkles initially formedin the label when the label is applied over curved surfaces and allowthe darts and wrinkles to be wiped down with minimal graphics distortionof the label. Films having unbalanced shrink, that is, films having ahigh degree of shrink in one direction and low to moderate shrink in theother direction are not particularly useful because while darts may beremoved in one direction, in the other direction the formation of dartsis exacerbated. Useful films having balanced shrink allow for a widervariety of label shapes to be applied to a wider variety of containershapes.

In one embodiment, the polymeric film has an ultimate shrinkage (S) asmeasured by ASTM procedure D1204 in at least one direction of at least10% at 90° C. and in the other direction, the shrinkage is S±20%. Inanother embodiment, the film has an ultimate shrinkage (S) in at leastone direction of about 10% to about 50% at 70° C. and in the otherdirection, the shrinkage is S±20%. In one embodiment, the ultimateshrinkage (S) is at least 10% at 90° C. and in the other direction, theshrinkage is S±10%. The shrink initiation temperature of the film, inone embodiment, is in the range of about 60° C. to about 80° C.

The shrink film must be thermally shrinkable and yet have sufficientstiffness to be dispensed using conventional labeling equipment andprocesses, including printing, die-cutting and label transfer. Thestiffness of the film required depends on the size of the label, thespeed of application and the labeling equipment being used. In oneembodiment, the shrink film has a stiffness in the machine direction(MD) of at least 5 mN, as measured by the L&W Bending Resistance test.In one embodiment, the shrink film has a stiffness of at least 10 mN, orat least 20 mN. The stiffness of the shrink film is important for properdispensing of labels over a peel plate at higher line speeds.

In one embodiment, the die-cut labels are applied to the article orcontainer in an automated labeling line process at a line speed of atleast 100 units per minute, or at least 250 units per minute or at least500 units per minute.

In one embodiment, the shrink film has a 2% secant modulus as measuredby ASTM D882 in the machine direction (MD) of about 20,000 to about400,000 psi, and in the transverse (or cross) direction (TD) of about20,000 to about 400,000 psi. In another embodiment, the 2% secantmodulus of the film is about 30,000 to about 300,000 in the machinedirection and about 30,000 to about 300,000 in the transverse direction.The film may have a lower modulus in the transverse direction than inthe machine direction so that the label is easily dispensed (MD) whilemaintaining sufficiently low modulus in the TD for conformability and/orsqueezability.

The polymeric film may be made by conventional processes. For example,the film may be produced using a double bubble process, tenter processor may comprise a blown film.

The shrink film useful in the label may be a single layer constructionor a multilayer construction. The layer or layers of the shrink film maybe formed from a polymer chosen from polyester, polyolefin, polyvinylchloride, polystyrene, polylactic acid, copolymers and blends thereof.

Polyolefins comprise homopolymers or copolymers of olefins that arealiphatic hydrocarbons having one or more carbon to carbon double bonds.Olefins include alkenes that comprise 1-alkenes, also known asalpha-olefins, such as 1-butene and internal alkenes having the carbonto carbon double bond on nonterminal carbon atoms of the carbon chain,such as 2-butene, cyclic olefins having one or more carbon to carbondouble bonds, such as cyclohexene and norbornadiene, and cyclic polyeneswhich are noncyclic aliphatic hydrocarbons having two or more carbon tocarbon double bonds, such as 1,4-butadiene and isoprene. Polyolefinscomprise alkene homopolymers from a single alkene monomer, such as apolypropylene homopolymer, alkene copolymers from at least one alkenemonomer and one or more additional olefin monomers where the firstlisted alkene is the major constituent of the copolymer, such as apropylene-ethylene copolymer and a propylene-ethylene-butadienecopolymer, cyclic olefin homopolymers from a single cyclic olefinmonomer, and cyclic olefin copolymers from at least one cyclic olefinmonomer and one or more additional olefin monomers wherein the firstlisted cyclic olefin is the major constituent of the copolymer, andmixtures of any of the foregoing olefin polymers.

In one embodiment, the shrink film is a multilayer film comprising acore layer and at least one skin layer. The skin layer may be aprintable skin layer. In one embodiment, the multilayer shrink filmcomprises a core and two skin layers, wherein in at least one skin layeris printable. The multilayer shrink film may be a coextruded film.

The film can range in thickness from 0.5-20, or 0.5-12, or 0.5-8, or 1-3mils. The difference in the layers of the film can include a differencein thermoplastic polymer components, in additive components, inorientation, in thickness, or a combination thereof. The thickness ofthe core layer can be 50-95%, or 60-95% or 70-90% of the thickness ofthe film. The thickness of a skin layer or of a combination of two skinlayers can be 5-50%, or 5-40% or 10-30% of the thickness of the film.

The film can be further treated on one surface or both the upper andlower surfaces to enhance performance in terms of printability oradhesion to an adhesive. The treatment can comprise applying a surfacecoating such as, for example, a lacquer, applying a high energydischarge to include a corona discharge to a surface, applying a flametreatment to a surface, or a combination of any of the foregoingtreatments. In an embodiment of the invention, the film is treated onboth surfaces, and in another embodiment the film is treated on onesurface with a corona discharge and is flame treated on the othersurface.

The layers of the shrink film may contain pigments, fillers,stabilizers, light protective agents or other suitable modifying agentsif desired. The film may also contain anti-block, slip additives andanti-static agents. Useful anti-block agents include inorganicparticles, such as clays, talc, calcium carbonate and glass. Slipadditives useful in the present invention include polysiloxanes, waxes,fatty amides, fatty acids, metal soaps and particulate such as silica,synthetic amorphous silica and polytetrafluoroethylene powder.Anti-static agents useful in the present invention include alkali metalsulfonates, polyether-modified polydiorganosiloxanes,polyalkylphenylsiloxanes and tertiary amines.

In one embodiment, the shrink film is microperforated to allow trappedair to be released from the interface between the label and the articleto which it is adhered. In another embodiment, the shrink film ispermeable to allow fluid to escape from the adhesive or from the surfaceof the article to escape. In one embodiment, vent holes or slits areprovided in the shrink film.

Adhesives

A description of useful pressure sensitive adhesives may be found inEncyclopedia of Polymer Science and Engineering, Vol. 13,Wiley-Interscience Publishers (New York, 1988). Additional descriptionof useful PSAs may be found in Polymer Science and Technology, Vol. 1,Interscience Publishers (New York, 1964). Conventional PSAs, includingacrylic-based PSAs, rubber-based PSAs and silicone-based PSAs areuseful. The PSA may be a solvent based or may be a water based adhesive.Hot melt adhesives may also be used. In one embodiment, the PSAcomprises an acrylic emulsion adhesive.

The adhesive and the side of the film to which the adhesive is appliedhave sufficient compatibility to enable good adhesive anchorage. In oneembodiment, the adhesive is chosen so that the labels may be cleanlyremoved from PET containers up to 24 hours after application. Theadhesive is also chosen so that the adhesive components do not migrateinto the film.

In one embodiment, the adhesive may be formed from an acrylic basedpolymer. It is contemplated that any acrylic based polymer capable offorming an adhesive layer with sufficient tack to adhere to a substratemay function in the present invention. In certain embodiments, theacrylic polymers for the pressure-sensitive adhesive layers includethose formed from polymerization of at least one alkyl acrylate monomercontaining from about 4 to about 12 carbon atoms in the alkyl group, andpresent in an amount from about 35-95% by weight of the polymer orcopolymer, as disclosed in U.S. Pat. No. 5,264,532. Optionally, theacrylic based pressure-sensitive adhesive might be formed from a singlepolymeric species.

The glass transition temperature of a PSA layer comprising acrylicpolymers can be varied by adjusting the amount of polar, or “hardmonomers”, in the copolymer, as taught by U.S. Pat. No. 5,264,532,incorporated herein by reference. The greater the percentage by weightof hard monomers is an acrylic copolymer, the higher the glasstransition temperature. Hard monomers contemplated useful for thepresent invention include vinyl esters, carboxylic acids, andmethacrylates, in concentrations by weight ranging from about zero toabout thirty-five percent by weight of the polymer.

The PSA can be acrylic based such as those taught in U.S. Pat. No.5,164,444 (acrylic emulsion), U.S. Pat. No. 5,623,011 (tackified acrylicemulsion) and U.S. Pat. No. 6,306,982. The adhesive can also berubber-based such as those taught in U.S. Pat. No. 5,705,551 (rubber hotmelt). It can also be radiation curable mixture of monomers withinitiators and other ingredients such as those taught in U.S. Pat. No.5,232,958 (UV cured acrylic) and U.S. Pat. No. 5,232,958 (EB cured). Thedisclosures of these patents as they relate to acrylic adhesives arehereby incorporated by reference.

Commercially available PSAs are useful in the invention. Examples ofthese adhesives include the hot melt PSAs available from H.B. FullerCompany, St. Paul, Minn. as HM-1597, HL-2207-X, HL-2115-X, HL-2193-X.Other useful commercially available PSAs include those available fromCentury Adhesives Corporation, Columbus, Ohio. Another useful acrylicPSA comprises a blend of emulsion polymer particles with dispersiontackifier particles as generally described in Example 2 of U.S. Pat. No.6,306,982. The polymer is made by emulsion polymerization of2-ethylhexyl acrylate, vinyl acetate, dioctyl maleate, and acrylic andmethacrylic comonomers as described in U.S. Pat. No. 5,164,444 resultingin the latex particle size of about 0.2 microns in weight averagediameters and a gel content of about 60%.

A commercial example of a hot melt adhesive is H2187-01, sold by AtoFindley, Inc., of Wauwatusa, Wis. In addition, rubber based blockcopolymer PSAs described in U.S. Pat. No. 3,239,478 also can be utilizedin the adhesive constructions of the present invention, and this patentis hereby incorporated by a reference for its disclosure of such hotmelt adhesives that are described more fully below.

In another embodiment, the pressure-sensitive adhesive comprises rubberbased elastomer materials containing useful rubber based elastomermaterials include linear, branched, grafted, or radial block copolymersrepresented by the diblock structure A--B, the triblock A--B--A, theradial or coupled structures (A--B)_(n), and combinations of these whereA represents a hard thermoplastic phase or block which is non-rubbery orglassy or crystalline at room temperature but fluid at highertemperatures, and B represents a soft block which is rubbery orelastomeric at service or room temperature. These thermoplasticelastomers may comprise from about 75% to about 95% by weight of rubberysegments and from about 5% to about 25% by weight of non-rubberysegments.

The non-rubbery segments or hard blocks comprise polymers of mono- andpolycyclic aromatic hydrocarbons, and more particularlyvinyl-substituted aromatic hydrocarbons that may be monocyclic orbicyclic in nature. Rubbery materials such as polyisoprene,polybutadiene, and styrene butadiene rubbers may be used to form therubbery block or segment. Particularly useful rubbery segments includepolydienes and saturated olefin rubbers of ethylene/butylene orethylene/propylene copolymers. The latter rubbers may be obtained fromthe corresponding unsaturated polyalkylene moieties such aspolybutadiene and polyisoprene by hydrogenation thereof.

The block copolymers of vinyl aromatic hydrocarbons and conjugateddienes that may be utilized include any of those that exhibitelastomeric properties. The block copolymers may be diblock, triblock,multiblock, starblock, polyblock or graftblock copolymers. Throughoutthis specification, the terms diblock, triblock, multiblock, polyblock,and graft or grafted-block with respect to the structural features ofblock copolymers are to be given their normal meaning as defined in theliterature such as in the Encyclopedia of Polymer Science andEngineering, Vol. 2, (1985) John Wiley & Sons, Inc., New York, pp.325-326, and by J. E. McGrath in Block Copolymers, Science Technology,Dale J. Meier, Ed., Harwood Academic Publishers, 1979, at pages 1-5.

Such block copolymers may contain various ratios of conjugated dienes tovinyl aromatic hydrocarbons including those containing up to about 40%by weight of vinyl aromatic hydrocarbon. Accordingly, multi-blockcopolymers may be utilized which are linear or radial symmetric orasymmetric and which have structures represented by the formulae A--B,A--B--A, A--B--A--B, B--A--B, (AB)_(0,1,2 . . .) BA, etc., wherein A isa polymer block of a vinyl aromatic hydrocarbon or a conjugateddiene/vinyl aromatic hydrocarbon tapered copolymer block, and B is arubbery polymer block of a conjugated diene.

The block copolymers may be prepared by any of the well-known blockpolymerization or copolymerization procedures including sequentialaddition of monomer, incremental addition of monomer, or couplingtechniques as illustrated in, for example, U.S. Pat. Nos. 3,251,905;3,390,207; 3,598,887; and 4,219,627. As well known, tapered copolymerblocks can be incorporated in the multi-block copolymers bycopolymerizing a mixture of conjugated diene and vinyl aromatichydrocarbon monomers utilizing the difference in their copolymerizationreactivity rates. Various patents describe the preparation ofmulti-block copolymers containing tapered copolymer blocks includingU.S. Pat. Nos. 3,251,905; 3,639,521; and 4,208,356, the disclosures ofwhich are hereby incorporated by reference.

Conjugated dienes that may be utilized to prepare the polymers andcopolymers are those containing from 4 to about 10 carbon atoms and moregenerally, from 4 to 6 carbon atoms. Examples include from1,3-butadiene, 2-methyl-1,3-butadiene(isoprene),2,3-dimethyl-1,3-butadiene, chloroprene, 1,3-pentadiene, 1,3-hexadiene,etc. Mixtures of these conjugated dienes also may be used.

Examples of vinyl aromatic hydrocarbons which may be utilized to preparethe copolymers include styrene and the various substituted styrenes suchas o-methylstyrene, p-methylstyrene, p-tert-butylstyrene,1,3-dimethylstyrene, alpha-methylstyrene, beta-methylstyrene,p-isopropylstyrene, 2,3-dimethylstyrene, o-chlorostyrene,p-chlorostyrene, o-bromostyrene, 2-chloro-4-methylstyrene, etc.

Many of the above-described copolymers of conjugated dienes and vinylaromatic compounds are commercially available. The number averagemolecular weight of the block copolymers, prior to hydrogenation, isfrom about 20,000 to about 500,000, or from about 40,000 to about300,000.

The average molecular weights of the individual blocks within thecopolymers may vary within certain limits. In most instances, the vinylaromatic block will have a number average molecular weight in the orderof about 2000 to about 125,000, or between about 4000 and 60,000. Theconjugated diene blocks either before or after hydrogenation will havenumber average molecular weights in the order of about 10,000 to about450,000, or from about 35,000 to 150,000.

Also, prior to hydrogenation, the vinyl content of the conjugated dieneportion generally is from about 10% to about 80%, or from about 25% toabout 65%, particularly 35% to 55% when it is desired that the modifiedblock copolymer exhibit rubbery elasticity. The vinyl content of theblock copolymer can be measured by means of nuclear magnetic resonance.

Specific examples of diblock copolymers include styrene-butadiene (SB),styrene-isoprene (SI), and the hydrogenated derivatives thereof.Examples of triblock polymers include styrene-butadiene-styrene (SBS),styrene-isoprene-styrene (SIS),alpha-methylstyrene-butadiene-alpha-methylstyrene, andalpha-methylstyrene-isoprene alpha-methylstyrene. Examples ofcommercially available block copolymers useful as the adhesives in thepresent invention include those available from Kraton Polymers LLC underthe KRATON trade name.

Upon hydrogenation of the SBS copolymers comprising a rubbery segment ofa mixture of 1,4 and 1,2 isomers, a styrene-ethylene-butylene styrene(SEBS) block copolymer is obtained. Similarly, hydrogenation of an SISpolymer yields a styrene-ethylene propylene-styrene (SEPS) blockcopolymer.

The selective hydrogenation of the block copolymers may be carried outby a variety of well known processes including hydrogenation in thepresence of such catalysts as Raney nickel, noble metals such asplatinum, palladium, etc., and soluble transition metal catalysts.Suitable hydrogenation processes which can be used are those wherein thediene-containing polymer or copolymer is dissolved in an inerthydrocarbon diluent such as cyclohexane and hydrogenated by reactionwith hydrogen in the presence of a soluble hydrogenation catalyst. Suchprocedures are described in U.S. Pat. Nos. 3,113,986 and 4,226,952, thedisclosures of which are incorporated herein by reference. Suchhydrogenation of the block copolymers which are carried out in a mannerand to extent as to produce selectively hydrogenated copolymers having aresidual unsaturation content in the polydiene block of from about 0.5%to about 20% of their original unsaturation content prior tohydrogenation.

In one embodiment, the conjugated diene portion of the block copolymeris at least 90% saturated and more often at least 95% saturated whilethe vinyl aromatic portion is not significantly hydrogenated.Particularly useful hydrogenated block copolymers are hydrogenatedproducts of the block copolymers of styrene—isoprene-styrene such as astyrene-(ethylene/propylene)-styrene block polymer. When apolystyrene-polybutadiene-polystyrene block copolymer is hydrogenated,it is desirable that the 1,2-polybutadiene to 1,4-polybutadiene ratio inthe polymer is from about 30:70 to about 70:30. When such a blockcopolymer is hydrogenated, the resulting product resembles a regularcopolymer block of ethylene and 1-butene (EB). As noted above, when theconjugated diene employed as isoprene, the resulting hydrogenatedproduct resembles a regular copolymer block of ethylene and propylene(EP).

A number of selectively hydrogenated block copolymers are availablecommercially from Kraton Polymers under the general trade designation“Kraton G.” One example is Kraton G1652 which is a hydrogenated SBStriblock comprising about 30% by weight of styrene end blocks and amidblock which is a copolymer of ethylene and 1-butene (EB). A lowermolecular weight version of G1652 is available under the designationKraton G1650. Kraton G1651 is another SEBS block copolymer whichcontains about 33% by weight of styrene. Kraton G1657 is an SEBS diblockcopolymer which contains about 13% w styrene. This styrene content islower than the styrene content in Kraton G1650 and Kraton G1652.

In another embodiment, the selectively hydrogenated block copolymer isof the formula:

B_(n)(AB)_(o)A_(p)

wherein n=0 or 1; o is 1 to 100; p is 0 or 1; each B prior tohydrogenation is predominantly a polymerized conjugated dienehydrocarbon block having a number average molecular weight of about20,000 to about 450,000; each A is predominantly a polymerized vinylaromatic hydrocarbon block having a number average molecular weight offrom about 2000 to about 115,000; the blocks of A constituting about 5%to about 95% by weight of the copolymer; and the unsaturation of theblock B is less than about 10% of the original unsaturation. In otherembodiments, the unsaturation of block B is reduced upon hydrogenationto less than 5% of its original value, and the average unsaturation ofthe hydrogenated block copolymer is reduced to less than 20% of itsoriginal value.

The block copolymers may also include functionalized polymers such asmay be obtained by reacting an alpha, beta-olefinically unsaturatedmonocarboxylic or dicarboxylic acid reagent onto selectivelyhydrogenated block copolymers of vinyl aromatic hydrocarbons andconjugated dienes as described above. The reaction of the carboxylicacid reagent in the graft block copolymer can be effected in solutionsor by a melt process in the presence of a free radical initiator.

The preparation of various selectively hydrogenated block copolymers ofconjugated dienes and vinyl aromatic hydrocarbons which have beengrafted with a carboxylic acid reagent is described in a number ofpatents including U.S. Pat. Nos. 4,578,429; 4,657,970; and 4,795,782,and the disclosures of these patents relating to grafted selectivelyhydrogenated block copolymers of conjugated dienes and vinyl aromaticcompounds, and the preparation of such compounds are hereby incorporatedby reference. U.S. Pat. No. 4,795,782 describes and gives examples ofthe preparation of the grafted block copolymers by the solution processand the melt process. U.S. Pat. No. 4,578,429 contains an example ofgrafting of Kraton G1652 (SEBS) polymer with maleic anhydride with2,5-dimethyl-2,5-di(t-butylperoxy) hexane by a melt reaction in a twinscrew extruder.

Examples of commercially available maleated selectively hydrogenatedcopolymers of styrene and butadiene include Kraton FG1901X, FG1921X, andFG1924X, often referred to as maleated selectively hydrogenated SEBScopolymers. FG1901X contains about 1.7% w bound functionality assuccinic anhydride and about 28% w of styrene. FG1921X contains about 1%w of bound functionality as succinic anhydride and 29% w of styrene.FG1924X contains about 13% styrene and about 1% bound functionality assuccinic anhydride.

Useful block copolymers also are available from Nippon Zeon Co., 2-1,Marunochi, Chiyoda-ku, Tokyo, Japan. For example, Quintac 3530 isavailable from Nippon Zeon and is believed to be a linearstyrene-isoprene-styrene block copolymer.

Unsaturated elastomeric polymers and other polymers and copolymers whichare not inherently tacky can be rendered tacky when compounded with anexternal tackifier. Tackifiers, are generally hydrocarbon resins, woodresins, rosins, rosin derivatives, and the like, which when present inconcentrations ranging from about 40% to about 90% by weight of thetotal adhesive composition, or from about 45% to about 85% by weight,impart pressure-sensitive adhesive characteristics to the elastomericpolymer adhesive formulation. Compositions containing less than about40% by weight of tackifier additive do not generally show sufficient“quickstick,” or initial adhesion, to function as a pressure-sensitiveadhesive, and therefore are not inherently tacky. Compositions with toohigh a concentration of tackifying additive, on the other hand,generally show too little cohesive strength to work properly in mostintended use applications of constructions made in accordance with theinstant invention.

It is contemplated that any tackifier known by those of skill in the artto be compatible with elastomeric polymer compositions may be used withthe present embodiment of the invention. One such tackifier, founduseful is Wingtak 10, a synthetic polyterpene resin that is liquid atroom temperature, and sold by the Goodyear Tire and Rubber Company ofAkron, Ohio. Wingtak 95 is a synthetic tackifier resin also availablefrom Goodyear that comprises predominantly a polymer derived frompiperylene and isoprene. Other suitable tackifying additives may includeEscorez 1310, an aliphatic hydrocarbon resin, and Escorez 2596, a C₅-C₉(aromatic modified aliphatic) resin, both manufactured by Exxon ofIrving, Tex. Of course, as can be appreciated by those of skill in theart, a variety of different tackifying additives may be used to practicethe present invention.

In addition to the tackifiers, other additives may be included in thePSAs to impart desired properties. For example, plasticizers may beincluded, and they are known to decrease the glass transitiontemperature of an adhesive composition containing elastomeric polymers.An example of a useful plasticizer is Shellflex 371, a naphthenicprocessing oil available from Shell Lubricants of Texas. Antioxidantsalso may be included on the adhesive compositions. Suitable antioxidantsinclude Irgafos 168 and Irganox 565 available from Ciba-Geigy,Hawthorne, N.Y. Cutting agents such as waxes and surfactants also may beincluded in the adhesives.

The pressure sensitive adhesive may be applied from a solvent, emulsionor suspension, or as a hot melt. The adhesive may be applied to theinner surface of the shrink film by any known method. For example, theadhesive may be applied by die coating curtain coating, spraying,dipping, rolling, gravure or flexographic techniques. The adhesive maybe applied to the shrink film in a continuous layer, a discontinuouslayer or in a pattern. The pattern coated adhesive layer substantiallycovers the entire inner surface of the film. As used herein,“substantially covers” is intended to mean the pattern in continuousover the film surface, and is not intended to include adhesive appliedonly in a strip along the leading or trailing edges of the film or as a“spot weld” on the film.

In one embodiment, an adhesive deadener is applied to portions of theadhesive layer to allow the label to adhere to complex shaped articles.In one embodiment, non-adhesive material such as ink dots or microbeadsare applied to at least a portion of the adhesive surface to allow theadhesive layer to slide on the surface of the article as the label isbeing applied and/or to allow air trapped at the interface between thelabel and the article to escape.

A single layer of adhesive may be used or multiple adhesive layers maybe used. Depending on the shrink film used and the article or containerto which the label is to be applied, it may be desirable to use a firstadhesive layer adjacent to the shrink film and a second adhesive layerhaving a different composition on the surface to be applied to thearticle or container for sufficient tack, peel strength and shearstrength.

In one embodiment, the pressure sensitive adhesive has sufficient shearor cohesive strength to prevent excessive shrink-back of the label whereadhered to the article upon the action of heat after placement of thelabel on the article, sufficient peel strength to prevent the film fromlabel from lifting from the article and sufficient tack or grab toenable adequate attachment of the label to the article during thelabeling operation. In one embodiment, the adhesive moves with the labelas the shrink film shrinks upon the application of heat. In anotherembodiment, the adhesive holds the label in position so that as theshrink film shrinks, the label does not move.

The heat shrinkable film may include other layers in addition to themonolayer or multilayer heat shrinkable polymeric film. In oneembodiment, a metalized coating of a thin metal film is deposited on thesurface of the polymeric film. The heat shrinkable film may also includea print layer on the polymer film. The print layer may be positionedbetween the heat shrink layer and the adhesive layer, or the print layermay be on the outer surface of the shrink layer. In one embodiment, thefilm is reverse printed with a design, image or text so that the printside of the skin is in direct contact with the container to which thefilm is applied. In this embodiment, the film is transparent.

The labels of the present invention may also contain a layer of anink-receptive composition that enhances the printability of thepolymeric shrink layer or metal layer if present, and the quality of theprint layer thus obtained. A variety of such compositions are known inthe art, and these compositions generally include a binder and apigment, such as silica or talc, dispersed in the binder. The presenceof the pigment decreases the drying time of some inks. Suchink-receptive compositions are described in U.S. Pat. No. 6,153,288(Shih et al) and the disclosure of this patent is hereby incorporated byreference.

The print layer may be an ink or graphics layer, and the print layer maybe a mono-colored or multi-colored print layer depending on the printedmessage and/or the intended pictorial design. These include variableimprinted data such as serial numbers, bar codes, trademarks, etc. Thethickness of the print layer is typically in the range of about 0.5 toabout 10 microns, and in one embodiment about 1 to about 5 microns, andin another embodiment about 3 microns. The inks used in the print layerinclude commercially available water-based, solvent-based orradiation-curable inks. Examples of these inks include Sun Sheen (aproduct of Sun Chemical identified as an alcohol dilutable polyamideink), Suntex MP (a product of Sun Chemical identified as a solvent-basedink formulated for surface printing acrylic coated substrates, PVDCcoated substrates and polyolefin films), X-Cel (a product of Water InkTechnologies identified as a water-based film ink for printing filmsubstrates), Uvilith AR-109 Rubine Red (a product of Daw Ink identifiedas a UV ink) and CLA91598F (a product of Sun Chemical identified as amultibond black solvent-based ink).

In one embodiment, the print layer comprises a polyester/vinyl ink, apolyamide ink, an acrylic ink and/or a polyester ink. The print layermay be formed in the conventional manner by, for example, gravure,flexographic or UV flexographic printing or the like, an ink compositioncomprising a resin of the type described above, a suitable pigment ordye and one or more suitable volatile solvents onto one or more desiredareas of the film. After application of the ink composition, thevolatile solvent component(s) of the ink composition evaporate(s),leaving only the non-volatile ink components to form the print layer.

The adhesion of the ink to the surface of the polymeric shrink film ormetal layer if present can be improved, if necessary, by techniques wellknown to those skilled in the art. For example, as mentioned above, anink primer or other ink adhesion promoter can be applied to the metallayer or the polymeric film layer before application of the ink.Alternatively the surface of the polymeric film can be corona treated orflame treated to improve the adhesion of the ink to the polymeric filmlayer.

Useful ink primers may be transparent or opaque and the primers may besolvent based or water-based. In one embodiment, the primers areradiation curable (e.g., UV). The ink primer may comprise a lacquer anda diluent. The lacquer may be comprised of one or more polyolefins,polyamides, polyesters, polyester copolymers, polyurethanes,polysulfones, polyvinylidine chloride, styrene-maleic anhydridecopolymers, styrene-acrylonitrile copolymers, ionomers based on sodiumor zinc salts or ethylene methacrylic acid, polymethyl methacrylates,acrylic polymers and copolymers, polycarbonates, polyacrylonitriles,ethylene-vinyl acetate copolymers, and mixtures of two or more thereof.Examples of the diluents that can be used include alcohols such asethanol, isopropanol and butanol; esters such as ethyl acetate, propylacetate and butyl acetate; aromatic hydrocarbons such as toluene andxylene; ketones such as acetone and methyl ethyl ketone; aliphatichydrocarbons such as heptane; and mixtures thereof. The ratio of lacquerto diluent is dependent on the viscosity required for application of theink primer, the selection of such viscosity being within the skill ofthe art. The ink primer layer may have a thickness of from about 1 toabout 4 microns or from about 1.5 to about 3 microns.

A transparent polymer protective topcoat or overcoat layer may bepresent in the labels of the invention. The protective topcoat orovercoat layer provide desirable properties to the label before andafter the label is affixed to a substrate such as a container. Thepresence of a transparent topcoat layer over the print layer may, insome embodiments provide additional properties such as antistaticproperties stiffness and/or weatherability, and the topcoat may protectthe print layer from, e.g., weather, sun, abrasion, moisture, water,etc. The transparent topcoat layer can enhance the properties of theunderlying print layer to provide a glossier and richer image. Theprotective transparent protective layer may also be designed to beabrasion resistant, radiation resistant (e.g, UV), chemically resistant,thermally resistant thereby protecting the label and, particularly theprint layer from degradation from such causes. The protective overcoatmay also contain antistatic agents, or anti-block agents to provide foreasier handling when the labels are being applied to containers at highspeeds. The protective layer may be applied to the print layer bytechniques known to those skilled in the art. The polymer film may bedeposited from a solution, applied as a preformed film (laminated to theprint layer), etc.

When a transparent topcoat or overcoat layer is present, it may have asingle layer or a multilayered structure. The thickness of theprotective layer is generally in the range of about 12.5 to about 125microns, and in one embodiment about 25 to about 75 microns. Examples ofthe topcoat layers are described in U.S. Pat. No. 6,106,982 which isincorporated herein by reference.

The protective layer may comprise polyolefins, thermoplastic polymers ofethylene and propylene, polyesters, polyurethanes, polyacryls,polymethacryls, epoxy, vinyl acetate homopolymers, co- or terpolymers,ionomers, and mixtures thereof.

The transparent protective layer may contain UV light absorbers and/orother light stabilizers. Among the UV light absorbers that are usefulare the hindered amine absorbers available from Ciba Specialty Chemicalunder the trade designations “Tinuvin”. The light stabilizers that canbe used include the hindered amine light stabilizers available from CibaSpecialty Chemical under the trade designations Tinuvin 111, Tinuvin.123, (bis-(1-octyloxy-2,2,6,6-tetramethyl-4-piperidinyl) sebacate;Tinuvin 622, (a dimethyl succinate polymer with4-hydroxy-2,2,6,6-tetramethyl-1-piperidniethanol); Tinuvin 770(bis-(2,2,6,6-tetramethyl-4-piperidinyl)-sebacate); and Tinuvin 783.Additional light stabilizers include the hindered amine lightstabilizers available from Ciba Specialty Chemical under the tradedesignation “Chemassorb”, especially Chemassorb 119 and Chemassorb 944.The concentration of the UV light absorber and/or light stabilizer is inthe range of up to about 2.5% by weight, and in one embodiment about0.05% to about 1% by weight.

The transparent protective layer may contain an antioxidant. Anyantioxidant useful in making thermoplastic films can be used. Theseinclude the hindered phenols and the organo phosphites. Examples includethose available from Ciba Specialty Chemical under the tradedesignations Irganox 1010, Irganox 1076 or Irgafos 168. Theconcentration of the antioxidant in the thermoplastic film compositionmay be in the range of up to about 2.5% by weight, and in one embodimentabout 0.05% to about 1% by weight.

A release liner may be adhered to the adhesive layer to protect theadhesive layer during transport, storage and handling prior toapplication of the label to a substrate. The liner allows for efficienthandling of an array of individual labels after the labels are die cutand the matrix is stripped from the layer of facestock material and upto the point where the individual labels are dispensed in sequence on alabeling line. The release liner may have an embossed surface and/orhave non-adhesive material, such as microbeads or printed ink dots,applied to the surface of the liner.

Process

The process of applying the labels to articles or containers involvesnon-traditional operations and equipment. The process begins withtraditional dispensing equipment that separates the label from therelease liner via a peel plate or tip that presents the label withexposed adhesive to the container or article to be decorated. Referringto FIGS. 6A to 6D, the label 62, which has a central portion 61 and aperipheral portion 63 surrounding the central portion and having anouter boundary defined by the label edges, is contacted to the container60 initially by applying pressure to the label in the central portion.Having the initial tack point(s) 64 located in a more central portion ofthe label rather than on the leading edge or peripheral portion of thelabel facilitates a more even distribution of any darts or wrinklesformed between the leading and trailing edges of the applied label. Thisin turn facilitates removal of the darts or wrinkles with theapplication of heat.

For those articles having both compound curves and relatively planarregions, the label may be initially contacted with the container not ona compound curve, but closer to or within a relatively planar area ofthe container surface.

In one embodiment, the label is pre-heated to soften the shrink filmand/or activate the adhesive layer.

Pressure is applied to the transferred label with a series of brushes,rollers, wipers, squeegees, pneumatic rollers, or walking beam in acenter outward direction, as indicated by arrows 65, to obtain intimatecontact between the label and the container or article. This process isreferred to herein as “wipe down” of the label. The center to edgewiping motion forces any air trapped beneath the label to the outeredges, as indicated by arrows 66, and creates smaller, more evenlydistributed darts at the edges of the label. As the label covers thecomplex curves of the article, excess label material accumulates in theform of darts, pleats, channeling, bubbling and other applicationdefects generally in the peripheral portion of the label. Heat isapplied to at least a portion of the label to fully and smoothly adherethe label to the container as shown in FIG. 6D.

In one embodiment, pressure is applied to the label using a walking beamsystem equipped with a foam roller or foam covered beam. The foam rolleror beam applies downward pressure in the longitudinal direction to thecentral region of the label and then proceeds to the outer edges of thelabel, directing any air trapped under the label and the pleats,wrinkles and/or other defects to the outer edges of the label. Thisembodiment is illustrated in FIG. 7, wherein container 70 having label71 applied thereto, is positioned on lower foam block 72 a of a walkingbeam. Upper foam block 72 b applies downward pressure onto label 71 oncontainer 70 to push air from under the central portion of the label tothe periphery of the label as label and container are compressed betweenthe foam blocks of the walking beam.

Once the label is applied and initial wipe down is completed, the excesslabel material darts and defects are eliminated by heating at least aportion the label to shrink the darts and/or wrinkles. The label may beheated via passage through a heat tunnel, forced air, steam tunnel,direct contact heat pads or forms. In one embodiment, the label isheated to a temperature of at least 40° C. In one embodiment, the labelis heated to at least 60° C., or at least 70° C., or at least 80° C.

A subsequent wipe down of the label may be performed to eliminate anyremaining darts or wrinkles in the label. Pressure is again applied tothe label in a center outward direction to the label. The second wipedown can be performed by a series of rollers, wipers, squeegees,brushes, pneumatic rollers or a walking beam. The subsequent wipe downmay be performed concurrently with the application of heat to the label,or subsequent to the application of heat.

When applying the label to an article or container, the label may beinitially tacked to the article by applying pressure in a contact regionof the label, and then applying pressure across the label in a directionto a first edge of the label. The contact region may be in the center ofthe label or may be proximate to a second edge of the label opposite tothe first edge. For example, initial contact may be made in the centerof the label and then pressure is applied in an outward direction to theedges or periphery of the label. Alternatively, initial contact may bemade near one edge of the label and then pressure applied across thelabel to the opposite edge of the label. When applying the label to thearticle or container, it is desirable to move the excess label material,i.e., the darts or wrinkles, to at least one label edge. The excessmaterial is typically moved in the direction of the compound curve(s),where the heat applied to the label will shrink the label and allow itto conform to the compound curve and eliminate any darts or wrinklesformed. Heat and pressure may be applied to the label simultaneously.

In one embodiment of the invention, the method of applying a label to anarticle includes the steps of: providing an article having a surfaceincluding at least one compound curve; providing a label including (i) aheat shrinkable film having an inner surface and an outer surface; and(ii) a layer of pressure sensitive adhesive on the inner surface of theheat shrinkable film, wherein the label has a first edge and a contactregion; contacting the adhesive layer in the contact region with thearticle; and applying heat and pressure simultaneously to the label in adirection from the contact region to the first edge such that the firstedge of the label adheres to article and the label shrinks to conform tothe compound curve of the article, wherein the heat and pressure areapplied by at least one hot air knife assembly including a source ofheated air, a flow control mechanism and one or more hot air knifeslots. The contact region may be located in or near the center of thelabel. Alternatively, the contact region may be proximate to a secondedge of the label opposite the first edge.

FIG. 8 illustrates an embodiment of the invention wherein a hot airknife assembly is used to apply the label to the article or container. Alabel may be applied to one or both sides of the container. For the sakeof simplicity of illustration, a label is applied only to one surface ofthe container of FIG. 8. The hot air knife assembly includes a source ofhot air, a flow control mechanism and one or more hot air knife slots.As shown in FIG. 8A, two hot air knife slots 84 a, 84 b direct hot airat a high velocity to the center region 83 c of the label 82. The label82 is first applied to the center region 83 c of the container 81 with astandard peel-tip dispensing process (not shown) with the leading edge(first edge 83 a) and trailing edge (second edge 83 b) not tacked down.The container with the label tacked thereto is transported to the airknife assembly via a conveyor. Depending on the size and configurationof the container, additional hot air knife slots and/or hot airassemblies may be used to apply heat and pressure to the label. As shownin FIG. 8B, the hot air knifes 84 a, 84 b are rotated outwardly todirect hot air from the center region of the label 83 c to the firstedge 83 a and second edge 83 b of the label 82. As the hot air is forcedagainst the label 82, the air between the label and the container 81 ispushed to the edges 83 a, 83 b of the label to smooth the label andeliminate or reduce air bubbles under the label. The hot air directed atthe label 82 softens the label and shrinks the label. The simultaneousapplication of heat and pressure from the air knife slots 84 a, 84 b tothe label forces the label 82 to conform to the surface of the container81, including the compound curve(s) of the container. An optionalsubsequent heating step may be used to further shrink the label. Anadvantage of this method is that there is no direct contact with thelabel so that surface imperfections are not likely to be imparted to thelabel. An advantage is the ability to obtain high speed processing dueto the excellent heat transfer to the label and the continuous heatrecovery of the air knife assembly. This method may be used to applylabels to a variety of container and article shapes without the need forre-tooling.

FIG. 9 illustrates an embodiment wherein multiple air knife slots and/orair knife assemblies are used to apply a label to a container or articlein a sequence of steps. A label may be applied to one or both sides ofthe container. For the sake of simplicity of illustration, a label isapplied only to one surface of the container of FIG. 9. The hot airknife assembly includes a source of hot air, a flow control mechanismand one or more hot air knife slots. In an initial stage shown in 9A, ahot air knife slot 94 directs hot air at a high velocity to the centerregion 93 c of the label 92. The label 92 is first applied to the centerregion 93 c of the container 91 with a standard peel-tip dispensingprocess (not shown) with the leading edge (first edge 93 a) and trailingedge (second edge 93 b) not tacked down. The container with the labeltacked thereto is transported to the air knife assembly via a conveyor.As shown in 9B, as the container 91 is transported by conveyor past theair knife slot 94, hot air is forced against the label 92 to the firstedge 93 a of the label, heating the label and causing it to conform tothe surface of the container 91, while second edge 93 b not conformedand/or tacked down. The container is then rotated about 180° as shown in9C. As shown in 9D, the container 91 with the label 92 adhered theretois then transported to a second hot air slot 95 that forces hot airagainst the label 92 from the center 93 c to the second edge 93 b of thelabel, heating the label and causing it to conform to the surface of thecontainer 91 as shown in 9E. Depending on the size and configuration ofthe container, additional hot air knife slots and/or hot air assembliesmay be used to apply heat and pressure to the label. An optionalsubsequent heating step may be used to further shrink the label.

The labeled article of the present invention may be used in a variety ofapplications, including, but not limited to personal care products,household chemical products, food and beverages, toys, electronics,pharmaceuticals, health care products, industrial products andappliances.

EXAMPLES

The following examples are intended only to illustrate methods andembodiments in accordance with the invention, and as such should not beconstrued as imposing limitations upon the claims.

Example 1

A pressure sensitive shrink label is constructed from a 3 mil thick lowdensity polyethylene multilayer shrink film designated CorrTuff fromSealed Air. The film is coated with an acrylic emulsion adhesive S692Nfrom Avery Dennison. The adhesive is carried on a paper Glassine BG-40silicone coated release liner. The label is oversized, having thedimensions of approximately 5×3.5 inches, which is 20% greater than theindustry standard recommended label size for the bottle to which thelabel is applied.

A 15 oz Johnson & Johnson Baby Lotion bottle having compound curves isfilled with water, capped and processed through a Label-Aire 9000 serieslabeler at 100 bottles per minute (BPM). The labeler has dual-feedscrews with matched speed top and lower belts with Label-Aire 2115-CDlabeler heads with high torque stepper motor drive. The labels arepressed down with a walking beam type wipe down apparatus providingstraight out, center outward forces to direct the trapped air beneaththe label and resultant dart/pleat defects to the edge of the label. Theoversized label as applied to the bottle initially results inunacceptable small darts and pleat defects around the perimeter of thelabel. The labeled bottle is then processed through a Leister hot forcedair, conveyor wipe down system at 100 bpm. High velocity 260° C. hot airheats the bottle and label to 50° C., shrinking and taking up the excesslabel material darts and pleats down to the bottle surface. The label iswiped down with a walking beam for good label contact. The darts shrinkand are easily wiped flat after application of heat.

The finished labeled bottle with larger label area and larger graphicscontent is smoothly wiped down without the darts, pleats, ridges orwrinkle defects present in typical pressure sensitive oversized labels.The darts do not return upon aging. Table 1 below shows the propertiesof the label components.

Example 2

In accordance with the process described in Example 1, a pressuresensitive shrink label constructed from a 2 mil thick polypropylenemultilayer shrink film designated CZPA 200 from Innovia is applied tothe bottle having compound curves. After initial wipe down, medium sizeddarts are formed. High velocity hot air heats the bottle and label to100° C. The darts shrink and are easily wiped flat after application ofheat. The darts do not return after aging.

Example 3

In accordance with the process described in Example 1, a pressuresensitive shrink label constructed from a 2 mil thick polylactic acidsingle layer shrink film designated EARTHFIRST PLA from PlasticSuppliers is applied to the bottle having compound curves. After initialwipe down, medium sized darts are formed. High velocity hot air heatsthe bottle and label to 70° C. The darts shrink and are easily wipedflat after application of heat. The darts do not return after aging.

Comparative Example 4

In accordance with the process described in Example 1, a pressuresensitive shrink label constructed from a 2 mil thick machine directionoriented polypropylene single layer roll-on-shrink-on film from AveryDennison is applied to the bottle having compound curves. High velocityhot air heats the bottle and label to 70° C. The darts formed at the topand bottom of the label shrink upon application of heat and are easilywiped down, while the darts formed at the leading and trailing edgesremain. The removed darts do not return upon aging.

Comparative Example 5

In accordance with the process described in Example 1, a pressuresensitive shrink label constructed from a 1.9 mil thick transversedirection oriented polyvinyl chloride single layer film designated PentaLabel from Kloeckner is applied to the bottle having compound curves.High velocity hot air heats the bottle and label to 60° C. The dartsformed at the leading and trailing edges of the label shrink uponapplication of heat and are easily wiped down, while the darts formed atthe top and bottom of the label remain. The removed darts do not returnupon aging.

Comparative Example 6

In accordance with the process described in Example 1, a pressuresensitive shrink label constructed from a 2 mil thick transversedirection oriented glycol modified polyethylene terephthalate (PETG)single layer film designated Fusion 1775E from Mitsubishi is applied tothe bottle having compound curves. High velocity hot air heats thebottle and label to 50° C. The darts formed at the leading and trailingedges of the label shrink upon application of heat and are easily wipeddown, while the darts formed at the top and bottom of the label remain.The removed darts do not return upon aging.

Comparative Example 7

In accordance with the process described in Example 1, a pressuresensitive shrink label constructed from a 1.4 mil thick machinedirection oriented polyvinyl chloride single layer film designatedMF-L243/01 from Kloechner is applied to the bottle having compoundcurves. High velocity hot air heats the bottle and label to 60° C. Thefilm does not conform to the container. Initial wipe down is poor withmany darts formed in all directions. The darts and ridges remain afterthe application of heat and a second wipe down. The film exhibitsexcessive shrink back.

Comparative Example 8

In accordance with the process described in Example 1, a pressuresensitive shrink label constructed from a 2.0 mil thick polypropylenemultilayer film designated BTNY from Vifan is applied to the bottlehaving compound curves. High velocity hot air heats the bottle and labelto 100° C. The darts formed do not shrink completely at high temperatureand do not entirely wipe down flat. The darts return upon aging.

Comparative Example 9

In accordance with the process described in Example 1, a pressuresensitive shrink label constructed from a 3.4 mil thick medium densitypolyethylene (MDPE) multilayer film designated PE 85 from Charter Filmsis applied to the bottle having compound curves. High velocity hot airheats the bottle and label to 100° C. The darts formed do not shrinkcompletely at high temperature and do not entirely wipe down flat. Thedarts return upon aging.

TABLE 1 Film Ult Tensile Ex. Grade Polymer Construction ProcessSuppliers Gauge (PSI) 1 CorrTuff LDPE single layer double Sealed Air 3.010,000 MD bubble 20,000 CD 2 CZPA 200 PP multi-layer double Innovia 2.020,000 MD bubble 22,000 CD 3 EARTHFIRST PLA Poly single layer blownPlastic Suppliers 2.0 8,000 MD Lactic 8,000 CD Acid Comp. Med ShrinkROSO Film PP single layer MDO Avery PPD 2.0 — 4 Comp. Penta Label 2.0mil PVC single layer TDO Kloeckner 1.9 7,200 MD 5 OT-M276/41, 71/9400,16,900 CD GLGL Comp. Fusion 2.0 mil 1775E PETG single layer TDOMitsubishi 2.0 7,250 MD 6 29,000 CD Comp. MF-L243/01 WHT PVC singlelayer MDO Kloechner 1.4 — 7 03/402-B Comp. BTNY PP multi-layer tenterVifan 2.0 40,000 MD 8 20,000 CD Comp. PE 85 MDPE multi-layer blownCharter Films 3.4 3,000 MD 9 3,500 CD L&W Modulus Stiffness Shrink:Shrink: Ex. (PSI) (mN) MD TD Adhesive Liner 1 30,000 MD 26 MD 40% (106C.) 49% (106 C.) S692N BG40 30,000 CD 24 CD 70% (120 C.) 69% (120 C.)glassine 2 100,000 MD 24 MD 10% (106 C.) 0% (106 C.) S692N 1.2 mil130.000 CD 18 CD 14% (120 C.) 10% (120 C.) PET 3 300,000 MD 44 MD 7%(106 C.) 12% (106 C.) S692N 1.2 mil 300,000 CD 60 CD 8% (120 C.) 14%(120 C.) PET Comp. 200,000 MD 30 MD 14% (106 C.) 0% (106 C.) S692N 1.2mil 4 123,000 CD 26 CD 23% (120 C.) 0% (120 C.) PET Comp. — 52 MD 4%(106 C.) 56% (106 C.) S692N BG40 5 36 CD glassine Comp. — 70 MD 6% (106C.) 66% (106 C.) S692N BG40 6 30 CD glassine Comp. 220,000 MD — 41% (106C.) 0% (106 C.) S3506 1.2 mil 7 150,000 CD 45% (120 C.) +3% (120 C.) PETComp. — 35 MD 2% (106 C.) 0% (106 C.) S692N BG40 8 65 CD 2% (120 C.) 2%(120 C.) glassine Comp. 75,000 MD 40 MD 0% (106 C.) 0% (106 C.) S692NBG40 9 60,000 CD 50 CD 4% (120 C.) 0% (120 C.) glassine

While the invention has been explained in relation to its preferredembodiments, it is to be understood that various modifications thereofwill become apparent to those skilled in the art upon reading thespecification. Therefore, it is to be under stood that the inventiondisclosed herein is intended to cover such modifications as fall withinthe scope of the appended claims.

1. A method of applying a label to an article, the method comprising:providing an article having a surface comprising at least one compoundcurve; providing a label comprising (i) a heat shrinkable film having aninner surface and an outer surface; and (ii) a layer of pressuresensitive adhesive on the inner surface of the heat shrinkable film,wherein the label has a first edge and a contact region; contacting theadhesive layer in the contact region of the label with the article; andapplying heat and pressure simultaneously to the label in a directionfrom the contact region to the first edge such that the first edge ofthe label adheres to the article and the label shrinks to conform to thecompound curve of the article, wherein the heat and pressure are appliedby at least one hot air knife assembly comprising a source of heatedair, a flow control mechanism and one or more hot air knife slots. 2.The method of claim 1 wherein the label comprises a center and a secondedge opposite the first edge, and the contact region is proximate to orin the center of the label.
 3. The method of claim 1 wherein the labelcomprises a second edge opposite the first edge and the contact regionis proximate to the second edge of the label.
 4. The method of claim 2wherein the hot air knife assembly comprises at least two hot air knifeslots that rotate outwardly from the center of the label to the firstand second edges to adhere the label to the article.
 5. The method ofclaim 2 wherein a first hot air knife slot applies heat and pressure tothe center of the label to the first edge of the label, and a second hotair knife slot applies heat and pressure to the center of the label tothe second edge of the label.
 6. The method of claim 5 furthercomprising rotating the article about 180° prior to the application ofheat and pressure by the second hot air knife slot to the label.
 7. Themethod of claim 1 wherein the label is provided with a release lineradhered to the adhesive layer and the method further comprisesseparating the release liner from the label prior to contacting thelabel with the article.
 8. The method of claim 1 wherein the label isheated to a temperature of at least 40° C.
 9. The method of claim 1wherein the heat shrinkable film comprises a film selected frompolyester, polyolefin, polyvinyl chloride, polystyrene, polylactic acid,copolymers thereof and blends thereof.
 10. The method of claim 1 whereinthe heat shrinkable film comprises a polyolefin.
 11. The method of claim1 wherein the heat shrinkable film comprises a multilayer film having acore layer and at least one skin layer.
 12. The method of claim 1wherein the stiffness of the film is at least 5 mN in the machinedirection.
 13. The method of claim 1 wherein the label further comprisesa print layer between the heat shrinkable film and the adhesive layer,wherein the heat shrinkable film is transparent.
 14. The method of claim1 wherein the label further comprises a print layer on the outer surfaceof the heat shrinkable film.
 15. The method of claim 14 wherein thelabel further comprises a protective layer overlying the print layer.16. The method of claim 1 wherein the adhesive layer comprises anemulsion adhesive.
 17. The method of claim 1 wherein the adhesive layercomprises a hot melt adhesive.
 18. The method of claim 1 wherein theadhesive layer comprises a solvent based adhesive.
 19. The method ofclaim 1 wherein the pressure sensitive adhesive layer is continuous. 20.The method of claim 1 wherein the pressure sensitive adhesive layer ispatterned and the pattern substantially covers the inner surface of thefilm.
 21. The method of claim 1 wherein the heat shrinkable film has amachine direction and a transverse direction, the film having anultimate shrinkage S in at least one direction of at least 10% at 90°C., wherein the shrinkage in the other direction is S±20%.
 22. Themethod of claim 1 further comprising heating the label subsequent to thesimultaneous application of heat and pressure to the label by the hotair knife assembly.